1. The Field of the Invention
The present invention relates to biological implant materials for repair and reconstruction of cartilage-based tissues. More specifically, the present invention relates to cartilage-derived implants, methods of producing cartilage-derived implants, and methods of use for cartilage-derived implants for repair and reconstruction of the nose, ear, trachea, articular surfaces and other cartilage-based tissues.
2. The Relevant Technology
Plastic surgery of the nose, or rhinoplasty, often requires the use of cartilaginous implants to reconstruct and repair the underlying structures that comprise the nose. For many surgeons, the preferred implant material is a patient's own septal, auricular, or costal cartilage (collectively referred to as autologous cartilage). However, there is a limited amount of available autologous cartilage for use in repair, and often there is not enough availability for a given procedure (particularly revision procedures). Accordingly, autologous cartilage often cannot provide a large enough segment of cartilage for a given type of repair procedure. The harvesting of cartilage is also a time consuming procedure that results in donor site morbidity. Elderly or other medically compromised patients often cannot withstand the extra anesthesia time or invasiveness associated with the harvesting procedure. Furthermore, although autologous cartilage does not cause a foreign body response, over time autologous cartilage can be resorbed by the body.
One alternative to autologous cartilage is a synthetic implant. Two examples of structural synthetic implant materials include porous high density polyethylene (pHDPE) and silicone. However, synthetic implants used in nasal reconstruction possess known deficiencies including high rates of extrusion, unnatural feel, significantly higher infection rates, the need for removal when infected, high rates of migration, and ultimately, failure rates higher than autologous cartilage grafting. Despite the critical need for implants, surgeons often avoid the use of synthetic implants.
Allogenic or donated human tissue is another option for nasal reconstruction. Cartilage from the rib (costal cartilage), can be recovered from a donor and then processed into a final implant material. Typically, the cartilage is rinsed with various solutions and then gamma irradiated. The disadvantages of this implant material likewise include the limited availability of donor human tissue supply. Furthermore, costal cartilage does not have the same mechanical feel and flexibility as nasal cartilage, human cell remnants in the cartilage retain the potential to be recognized as a foreign body, and costal cartilage implants exhibit high rates of warping, making allogenic or donated human tissue an impractical and undesirable alternative.
Materials for use in some medical therapies may also be derived from animal tissue sources. The animal-derived source material is typically processed in a way that is intended to make the material compatible with the human body. These processing methods may include steps to remove cellular and antigenic substances from the source materials, crosslinking, and sterilization. However, known processing methods often include the use of harsh alcohols and detergent that irreversibly dry and damage cartilage by harming the molecular components, alter the biochemical or biomechanical properties of the cartilage, require excessive processing times, and employ additional expensive antibiotic components. Likewise, known methods of crosslinking (to protect the tissue from degradation when implanted into a human) may result in a change in mechanical properties and results in a change in how the body reacts to the tissue. These reactions can include calcification, excessive fibrous tissue deposition, and rejection. Cartilage, in particular, has biochemical and biomechanical properties that make the tissue particularly sensitive to current processing techniques.
Accordingly, there are a number of disadvantages in conventional cartilage-derived implants that can be addressed.